JPS5815666A - Processing method - Google Patents

Abstract

PURPOSE:To give the processing liquid abrasive grain sortability without using super-corpuscular particle in such a way that abrasive grain of hard and friable material is suspended in the processing liquid made by adding aqueous soluble liquid which improves viscosity into water, and both sides of a work are simultaneously ground by means of the suspension liquid. CONSTITUTION:Viscous polisher 4 is adhered on upper and lower fixing discs 11, 12, while a constant load is being applied through processing liquid 14 in which viscosity is improved and abrasive grain 13 is suspended, a work 1 is made planetary revolution by means of a carrier 15 therein. If viscosity of the processing liquid, since according to the Stokes' law, bigger abrasive grain undergoes more restricted movement in the fluid, by properly sorting the viscosity, the size of abrasive grain to take part in the processing can be sorted. Thus, the surfaces of the work can be finished to be non-turbulent surfaces at the same time on its both sides.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for processing hard and brittle materials using free abrasive grains.

Conventional techniques for polishing glass substrates with high precision and quality include ■ A method of processing using free abrasive grains ranging from coarse particles to ultra-fine particles; ■ A method of immersing the workpiece in a machining fluid and mixing the abrasive grains and the machining fluid. There is a method of processing a metal surface plate, etc. and a workpiece in a non-contact state with the metal surface plate interposed therebetween.

In the former, as shown in FIGS. 1 to 5, abrasive grains 3 made of coarse particles are interposed between the workpiece 1 and the metal surface plate 2 (see FIGS. 1 and 2). (Fig.) for rough finishing. Further, the workpiece 1 is polished by a viscoelastic polisher 4 made of rubber or the like through abrasive grains 3' made of fine particles (see Figs. 3 and 4).
(Fig.), super-finishing I, and finally super-finishing (2) using abrasive grains 31 made of ultra-fine particles (5th v! J), thereby performing polishing in about five stages.

In this way, while changing the type of surface plate and abrasive grains, the workpiece is micro-scratched by mechanical or mechanical + chemical action, and a uniform surface without a stress-altered layer (hereinafter referred to as a non-porous surface) It is something that will be completed.

In the latter case, the workpiece 1 that has undergone superfinishing I is glued to a holding table 5, immersed in a water tank 7 filled with a machining liquid 6 containing abrasive grains 31, and placed on a rotating metal mold 2. The metal surface plate 2 and the workpiece 1 are rotated to maintain non-contact with each other in a fluid bearing state, and the unevenness of the workpiece 1 is removed on a molecular order, thereby finishing the surface of the hole.

However, in the former case, super-finishing I is performed before super-finishing ■, which results in a large number of steps and is inefficient.
Keep the water and environment used for processing clean (for example, use pure water).

For the atmosphere, we used a clean booth etc. for 7 to 10 hours.
, 000), and in addition, the ultrafine particles must have a uniform particle size, that is, the maximum particle size is usually 5 to 6 times the average particle size, but this must be within 3 times. All of the above conditions must be met. The disadvantage is that the required pore surface cannot be obtained. In addition, in the case of ultrafine particles of about 0.04μ,
Processing speed for borosilicate glass is 15A/se
It is about c.

Even in the latter case, since the order of processing is in molecular units, the processing efficiency is poor at about 1 alOA/sec, the equipment is large-scale, and another drawback is that simultaneous processing of both sides of a plate or the like is impossible.

By the way, when aiming for high efficiency in free abrasive processing of hard and brittle materials, microscratches due to the mechanical action of abrasive grains,
A stress-altered layer is likely to occur -0 Therefore, processing is performed using mechanical and chemical effects using ultrafine particles, submerged processing, etc., but in this case, the processing environment, particle size distribution of abrasive grains, equipment, etc. are severe. Extracting requires certain conditions, and results can only be obtained with low efficiency.

The present invention was made as a result of intensive research in order to eliminate the above-mentioned drawbacks of the conventional technology.It gives the machining fluid the ability to select abrasive grains without using ultrafine particles, and eliminates abnormal abrasive grains or foreign matter from being involved in machining. The purpose is to prevent this from occurring, and to minimize its influence even if it is involved, and to finish the surface of one workpiece simultaneously on both sides with a hole-free surface.

Furthermore, it is possible to perform superfinishing I and I in the conventional example in one step, thereby streamlining the process.

In other words, the present invention suspends abrasive grains of a hard brittle material in a machining liquid made by adding a water-soluble liquid that increases viscosity to water, and simultaneously polishes both sides of a workpiece with the suspension. The movement of abrasive grains in the machining fluid is controlled by the particle size of the abrasive grains.
This is a processing method in which the processing fluid has the ability to select whether it is involved in processing or not. This is Stokes' law
When a sphere with radius r is moving at speed v8 in a fluid with viscosity η, and the resistance force that the sphere receives is P, then P=6πηrv
o holds true. ”, in which case the viscosity η
If the abrasive grains are increased in size, the movement of large abrasive grains will be restricted in the fluid, so by appropriately adjusting the viscosity, it is possible to select the size of the abrasive grains (including foreign substances) involved in processing.

Furthermore, if abrasive grains with a size outside (or above) the above constraints are involved in machining and abnormal abrasive grains are interposed between the surface plate and the workpiece, the machining fluid will concentrate on the abnormal abrasive grains. It has the function of dispersing this load, and is characterized by preventing the occurrence of micro-scratches and stress-altered layers caused by abnormal abrasive grains on the workpiece.

Next, one embodiment of the present invention will be explained based on the drawings.
In the cross section IW in the figure, the viscoelastic lisha 4 is placed on the upper and lower surface plates 1.
1.12, and while applying a constant load through a machining fluid 14 with increased viscosity and suspension of abrasive grains 13, the workpiece 1 is planetarily rotated by a carrier 15 to form φ. Ru. Of course, it is necessary to continuously supply the machining liquid 14 in which abrasive grains are suspended through the supply hole 16 provided in the upper surface plate 11, and in this way, the surface of the workpiece is coated by mechanical and chemical actions. It can be finished to a mirror-like orifice-like surface.

The abrasive grains used in the present invention include those with an average particle size of 0.5 μm and a particle size of 3 μm, which is 6 times the average grain size.

This particle size distribution is shown in FIG.

At this time, abrasive grain #i zirconium oxide (zroz) was used, but alumina (htt O,), magnesium oxide (MgO), cerium oxide (OeO, >
FetO3), zinc oxide (ZnO), Y oxide (M
nO), boron carbide (B4C), diamond, etc. can also be used. In FIG. 8, 2% by weight of the total particles had a particle diameter of 3 microns, which is six times the average particle diameter of 0.5 microns, and particles with a particle diameter of 3 microns to 8 microns were also observed.

The water used #i is 3 μl filtered and not ion-exchanged, and the viscosity is increased by adding ethylene glyfur.

Ethylene glycol F! 20CP (centipoise, 20
It has a viscosity of °CI Po1se = 10 NSM'-), and the effects of the present invention can be seen if it is added to pure water in an amount of about (9) to gloss weight. Of course, the blending ratio differs slightly depending on the type of workpiece, for example, soda lime glass, borosilicate glass, quartz glass - acid resistance in the case of glass substrates for photomask blanks.

Figure 9 shows the viscosity of the machining fluid and the machining efficiency as a graph.
The upper column of the horizontal axis shows the viscosity (cp) including abrasive grains, and the lower column shows the amount (% by weight) of ethylene glycol in the processing liquid showing the viscosity in the upper column.

The following table shows the machining speed in the method of the present invention in comparison with that in the conventional example (2). The target is glass substrates for photomask blanks.

Table 1 As shown in Table 1 above, each has a considerably high efficiency as a super finishing.

The water-soluble liquid that increases the viscosity may be not only the above-mentioned ethylene glycol, but also any water-soluble liquid with a higher viscosity than water, but if the viscosity is not very high, add it until the effect is achieved. In this case, the amount added becomes high, so ethylene glycol, glycerin, etc. that exhibit 200 P or more at room temperature are desirable.

Workpieces to which the processing method of the present invention can be applied include not only glass substrates as described above, but also metal single crystals, polycrystalline materials, etc. If the optimum abrasive grain, grain size, etc. are selected according to the material, good.

Since the present invention is configured as described above, the obtained workpiece has uniform mechanical and chemical effects of abrasive grains, and there are no microscratches at all, and even if etched, there will be no bits or scratches. A surface with no turbulence can be obtained. This is shown in FIGS. 10 to 15. each first
FIGS. 0 to 12 are micrographs of the conventional example, and FIGS. 13 to 15 are micrographs (50 times magnification) of surface etching aids of glass substrates for photomask blanks obtained by the method of the present invention. The scratches that can be seen here and there in FIGS. 10 to 12 are completely visible in FIGS. 13 to 15, where the method of the present invention is applied.

Table 2 As shown above, the present invention is highly efficient because it does not use ultrafine particles, and the processing environment and particle size distribution of the abrasive grains are not a concern, making it easy and highly efficient to avoid disturbances. A surface is obtained. In addition to streamlining the process, it also has the remarkable effect of eliminating the need for large-scale equipment in the submerged lapping method and allowing simultaneous polishing of both sides.

[Brief explanation of the drawing]

Figures 1 to 5 are cross-sectional views of main parts showing the processing steps of conventional example (2), Figure 6 are cross-sectional views of main parts of the processing method of conventional example (2), and Figure 7 is a cross-sectional view of main parts of the processing method of the present invention. Figure 8 is a graph showing the particle size distribution of abrasive grains (ZrO,) used in the present invention, Figure 9 is a graph showing the viscosity and machining efficiency of the working fluid of the present invention, and Figure 10 is 12 to 12 are micrographs showing the surface conditions of glass substrates for photomask blanks obtained by the conventional processing method, and FIGS. 13 to 15 are micrographs in the case of the present invention. 1... Workpiece 2... Metal surface plate 3.13.
... Abrasive grains 4 ... Viscoelastic lisha 11, 12
...Surface plate 14-...Working liquid 15...Carrier 16...Supply water patent applicant Co., Ltd.
Hoya Electronics Figure 1, 14th flash () 1981, 157 days...“
2- From,・-'-Meibiru Address: 3280 Nakamaru, Nagaita-cho, Kitakoma-gun, Yamanashi Prefecture
Name: Hoya Electronics Co., Ltd. 4 Agent Published by ■, page 9, line 11 to line 18 of the specification, ``I can't see this at all.'' is deleted. 2. Table 2 on page 10 of the specification is revised as follows. Table 1-2 * Workpiece Comparative Example 1 Soda Lime Glass Comparative Example 2 Borosilicate Glass Comparative Example 3 Quartz Glass Example 1 Soda Rhino, Glass Example 2 Borosilicate Glass 3, Specification No. 1100, Lines 7 to 1 Delete ", Figure 1O...Micrograph" in line 1O. 4. Delete "Figures 10 to 15" in the drawings. 5.Reference photo/explanation of reference drawing (photo) separately
Submit with. that's all

Claims (1)

[Scope of Claims] 1) A method of suspending abrasive grains of hard brittle material in a machining liquid made by adding a water-soluble liquid that increases viscosity to water, and simultaneously polishing both sides of a workpiece with this suspension. A processing method characterized by 2) The processing method according to claim 1, wherein the viscosity-increasing water-soluble liquid has a viscosity of IOP or higher at room temperature. 3) The processing method according to claim 2, wherein the water-soluble liquid that increases viscosity is ethylene glycol. 4) The processing method according to claim 3, wherein 30-50% by weight of ethylene glycol is added to water.